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Area Forecast Discussion (AFD)

Issued by Eureka, CA (EKA)

FXUS66 KEKA 172120

National Weather Service Eureka CA
220 PM PDT Wed Oct 17 2018

.SYNOPSIS...Dry and mild afternoons accompanied by chilly nights 
will persist through the week across interior northwest 
California. Meanwhile, periods of low clouds and cooler afternoon 
temperatures are expected along the coast. Otherwise, rain chances
are forecast to increase next week.


.DISCUSSION...A blocked upper-air pattern persists across the WRN
CONUS as of Wednesday afternoon. A pair of quasi-stationary upper
lows were situated south of the EKA region...one offshore from SRN
CA, and a second centered over SRN UT/NRN AZ. Meanwhile, an upper
ridge was located over the NERN PAC, which was generally aiding
in large-scale subsidence over NWRN CA. Subsidence aloft was
yielding widespread clear skies over interior portions of NRN CA,
while weak high pressure located offshore from CA was aiding in
coastal northerlies and stubborn marine stratus. The stratus has
made attempts at clearing along the coast WED afternoon, but will
almost assuredly spread inland toward the WRN slopes of the
coastal mountains WED night...followed by a continued cycle of
partial clearing during Thursday and then redevelopment THU night.

Otherwise, clear skies occurring across wind sheltered valleys 
will support strong radiational cooling tonight and probable frost
development. Reference the latest frost advisory for additional 

Model guidance shows a pattern change taking place late this
weekend into early next week. A cold upper trough is forecast to
deepen over the Gulf of Alaska, which will aid in breaking down
the previously mentioned ridge and kick out the SWRN CONUS upper
low. A shortwave trough and associated surface frontal wave are
then forecast to move east across the PAC NW during Tuesday. The
frontal wave is forecast to yield rain, possibly moderate in
intensity over Humboldt and Del Norte Counties, by midday Tuesday
through Tuesday evening. A second rain-producing frontal wave is
then forecast to enter the area Wednesday afternoon.


.AVIATION...Marine stratus persisted all day along the Coast. The
result was areas of IFR/LIFR Cigs/VIS being reported into 
afternoon at ACV, CEC and other coastal airports as conditions 
continued to blanket the immediate coastline. Any scattering along
the coast today will be somewhat shortlived. The Inland empire 
will remain VFR and mostly SKC except for pockets of smoked 
associated with any fires or any prescribed burns. /TA


.MARINE...Weak high pressure over the northeastern Pacific will
favor northerly winds from 5 to 15 kt through the weekend. 
Otherwise, a long period west-northwesterly swell from 5 to 7 feet
at 14-17 seconds will persist into Friday, while a south-
southwesterly swell near 3 feet at 16 seconds will continue 
through the weekend. In the extended range, a frontal wave is 
forecast to move across the region next Tuesday and Wednesday. 
This feature may yield a period of rain and gusty south winds.


.BEACH HAZARDS...Hazardous beach conditions will be possible
through Wednesday night due to a long period northwesterly swell.
Surf heights from 9 to 12 feet will be possible for west- 
northwest facing beaches. In addition, the threat for sneaker 
waves will be elevated, especially for steep beaches. Beach goers 
should stay further away from the ocean and never turn their back 
to the ocean as hazardous waves can wash farther up the beach at 
any time.


.FIRE WEATHER...Warm temperatures and low humidity values will 
persist across the interior through the weekend. In addition, 
winds will occasionally become gusty out of the east across 
exposed ridges, especially from Thursday night through Saturday 
afternoon. Otherwise, winds will be light and terrain driven over 
the valleys. In the extended range, rain chances will increase 
next Tuesday and Wednesday.


CA...Beach Hazards Statement until 11 PM PDT this evening for 

     Frost Advisory from 1 AM to 9 AM PDT Thursday for CAZ102-104-106-



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